Simple JSON example not working

Hi everyone,

I have a simple module, but it's not functioning. I cannot seem to get any JSON data to be received/sent correctly.

Here is the code:
artplatform.module:

// $Id$ 
/** 
*@file 
*Art Platform 
*/ 

/** 
* Implementation of hook_perm(). 
* Permissions hook function
*/ 
function artplatform_perm() { 
	return array('search artwork'); 
} 

/** 
*Implementation of hook_menu(). 
*/ 
function artplatform_menu() { 
	$items['artwork/searchartwork'] = array( 
		'page callback' => 'searchartworkcontent', 
		'access arguments' => array('search artwork'), 
		'type'	=> MENU_CALLBACK, 
	); 
	return $items; 
} 

/** 
* Search DB for artwork
*/ 

function searchartworkcontent() {
	
	$termIDvar = 0;
	$nodeIDvar = '';
	
	if (!empty($_POST['artworkType'])) {
	
		$termIDvar = $_POST['artworkType'];
		$nodeIDvar = db_result(db_query("SELECT node.nid AS nid FROM node node	 INNER JOIN term_node term_node ON node.vid = term_node.vid WHERE (node.status <> 0) AND (node.type in ('artwork')) AND (term_node.tid = '".$termIDvar."')")); // Obtained via views module
	
		return drupal_json(array('nodeIDvar'=>$nodeIDvar));
exit();
	} else {
		return drupal_json(array('nodeIDvar'=>'no search yet.'));
exit();
	}
}


/** 
*Create widget to display on the web page. 
*/ 
function searchartworkcontent_widget() { 
	return theme('searchartworkcontent_widget'); 
} 


/** 
*Implementation of hook_theme(). 
*LetDrupalknowaboutourthemefunction. 
*/ 
function artplatform_theme() { 
	return array( 
		'searchartworkcontent_widget' => array( 
		'arguments'=>array(), 
		), 
	); 
} 

/** 
*Theme for artwork platform. 
*/ 
function theme_searchartworkcontent_widget() { 
	// Load the JavaScript and CSS files.  
	drupal_add_js(drupal_get_path('module', 'artplatform') .'/artplatform.js');
	$output = '<div class="search_results"></div>'; 
	return $output; 
} 




/** 
* Implementation of hook_nodeapi(). 
* Show content in node
*/ 
function artplatform_nodeapi(&$node, $op, $teaser, $page) { 
	switch ($op) { 
		case 'view': 
		if(!$teaser){ 
			$node->content['searchartworkcontent_widget']=array( 
				'#value' => searchartworkcontent_widget(), 
				'#weight'=>0, 
			);
		} 
		break; 
	} 
} 

And the JS file artplatform.js:

// $Id$ 
//Only run if we are in a supported browser. 
if(Drupal.jsEnabled) { 
//Run the following code when the DOM has been fully loaded. 
	$(document).ready(function() { 
		
		$('div.search_results').fadeTo('slow', 0);
		
		$('input:radio').click(function(){

			$('div.artworkSearchResult').html('Sending...').fadeTo('slow', 0);

			$.ajax({
				type: 'POST',
				url: this.href,
				data: $('input:radio').serialize(),
				dataType: 'json',
				success: function(data) { alert(Drupal.t("Yes ") + data.nodeIDvar); $('div. search_results').html(data.nodeIDvar).fadeTo('slow', 1); },
				error: function(xmlhttp) { alert(Drupal.t("An error occurred @ ") + xmlhttp.readyState); }
			});
			return false;	
		});
	}); 
} 

Via the ajax function I get a readystate of 4 and a status of 200 meaning that everything should be okay... but nothing is happening.
I have a list of taxonomy terms with radio buttons. When clicked, I want to get their value, and then display the $nid value for the nodes that contain the taxonomie term.

Any help would be much appreciated.